Hinge polymer

ABSTRACT

A polymer suitable for use in a thin film hinge (living hinge) comprising from about 0.1 to about 5 weight % of a C 4-8  comonomer and the balance ethylene, said composition having a density as determined according to ASTM D 792 from about 0.945 to about 0.965 g/cm 3 ; a melt index as determined according to ASTM D1238 (2.16 kg/190° C.) from about 10 to about 20 g/10 min; a weight average molecular weight (Mw) from about 45,000 to about 55,000 g/mol; a polydispersity from about 2.5 to about 3.1 and when molded into a strip having a length of about 13 cm and gross thickness from about 50 to about 70 mil (about 1 to about 2 mm) and completely bent over end to end four times to create a thinned region or crease having a thickness from about 15 to about 30 mil (about 0.3 to about 0.7 mm) tested by bending and releasing the deformed thinned region of the strip through a radius of curvature from about 180 to about 190° about a rounded plate goes through not less than 500 cycles without breaking.

CROSS REFERENCE TO RELATED PATENT APPLICATION

This application is a continuation of U.S. application Ser. No.14/205,628, filed on Mar. 12, 2014, entitled “Hinge Polymer”, which is anon-provisional of U.S. Application Ser. No. 61/782,869, filed on Mar.14, 2014, entitled “Hinge Polymer”, which are herein incorporated byreference in their entirety.

FIELD OF TECHNOLOGY

Described herein are tough moldable polyethylenes. There are a number ofapplications where a thin molded polyethylene part is required to haveexcellent resistance to flex cracking. That is the part may be flexed orbent a number of times without breaking. One example is lids fordispensing containers such as condiments, spices, soaps, shampoos, oilsand pills. The hinges for the lids need to have a life cycle of at leastabout 300 openings and closing before failure (e.g., the hinge breaks).

BACKGROUND

Currently, to the best of Applicants' knowledge, “snap top” dispensinglids are made from polypropylene due to its toughness. Whilepolyethylene has been disclosed as being suitable it is not used inthese applications. However, it is desirable from a recycling point ofview to use polyethylene rather than polypropylene.

U.S. Pat. No. 4,047,495, issued Sep. 13, 1977 to O'Brian, assigned toPolytop Corporation teaches a “snap top” child proof lid for acontainer. The patent teaches the living hinge is preferably injectionmolded from polypropylene because of the well-known living hingeproperties of polypropylene. Other olefin polymers can be used but arenot preferred (Col. 4, lines 41-50). The patent teaches away from otherpolyolefins, such as polyethylene.

U.S. Pat. No. 4,638,916, issued Jan. 27, 1987 to Beck et al., assignedto Owens-Illinois, Inc., teaches a snap type hinge cap. The structuralelements of the lid are disclosed but there is no disclosure of whatmaterial the lid may be made from. One of ordinary skill in the artwould likely select polypropylene as the preferred material.

U.S. Pat. No. 5,148,912, issued Sep. 22, 1992 to Nozawa, assigned toYoshino Kogyosho Co., Ltd., teaches a slightly different snap top lid inwhich there are two separate hinges or straps. Again the structuralelements are clearly defined but the composition of the cap is notclearly specified. One of ordinary skill in the art would likely selectpolypropylene as the preferred material.

U.S. Pat. No. 6,041,477, issued Mar. 28, 2000 to Rentsch et al., alsoteaches the structural elements of a snap top lid which differ from theprior art. While the patent contains a warning about residual stress insnap top lids having adverse effects on injection moulding plasticmaterial, (Col. 3, lines 28 to 35), nowhere in the specification isthere a disclosure of suitable materials from which to make the hinge.

U.S. Pat. No. 6,766,926, issued Jul. 27, 2004 to Elchert, assigned toOwens-Illinois Closure Inc., teaches the type of closure most commonlyseen to-day. The structural elements of the cap are clearly disclosed.However, again the material form which the cap may be made is notdiscussed.

A need exists to provide a polyethylene composition suitable for use ininjection molding having a high resistance to cracking on repeatedflexing.

SUMMARY

In its broadest embodiment, the present invention provides apolyethylene composition comprising from about 0.1 to about 5 weight %of a C₄₋₈ comonomer and the balance ethylene, said composition having adensity as determined according to ASTM D 792 from about 0.945 to about0.965 g/cm³; a melt index as determined according to ASTM D1238 (2.16kg/190° C.) from about 10 to about 20 g/10 min; a weight averagemolecular weight (Mw) from about 45,000 to about 55,000 g/mol; apolydispersity from about 2.5 to about 3.1 and when molded into a striphaving a length of about 13 cm (about 5.11 inches), a gross thicknessfrom about 50 to about 70 mil (thousandth of an inch) (about 1 to about2 mm) and bent over end to end and released four times to create athinned region having a thickness from about 15 to about 30 mil(thousandths of an inch) (about 0.3 to about 0.7 mm) tested by bendingand releasing the deformed thinned region of the strip through a radiusof curvature of about 180° to about 190°, about a plate having a roundededge goes through not less than 200 cycles without breaking, preferablynot less than 500 cycles without breaking.

In a further embodiment, the polyethylene composition has a density asdetermined according to ASTM D 792 from about 0.950 to about 0.960g/cm³.

In a further embodiment, the polyethylene composition has a melt indexas determined according to ASTM D1238 (2.16 kg/190° C.) from about 13 toabout 17 g/10 min.

In a further embodiment, the polyethylene composition when molded into astrip as above and tested as above goes through not less than 750 cycleswithout breaking.

In a further embodiment, the polyethylene composition has a lowercomonomer content at higher molecular weight.

In a further embodiment, the polyethylene composition is prepared fromone or more solution polymerized polyethylene(s).

In a further embodiment, the polyethylene composition comprises fromabout 60 to about 90 weight % of copolymer of ethylene and 1-butenehaving a density from about 0.945 to about 0.950 g/cm³ as determinedaccording to ASTM D 792; a melt index as determined according to ASTMD1238 (2.16 kg/190° C.) from about 15 to about 20 g/10 min; a weightaverage molecular weight (Mw) from about 45,000 to about 55,000; and apolydispersity from about 2.7 to about 3.0.

In a further embodiment, the polyethylene composition comprises of fromabout 40 to about 10 weight % of an ethylene homopolymer having adensity from about 0.955 to about 0.965 g/cm³ as determined according toASTM D 792; a melt index as determined according to ASTM D1238 (2.16kg/190° C.) from about 10 to about 15 g/10 min, a weight averagemolecular weight (Mw) from about 55,000 to about 65,000 and apolydispersity from about 3.1 to about 3.3.

In a further embodiment, the polyethylene composition consisting of fromabout 60 to about 80 weight % of copolymer of ethylene and 1-butenehaving a density from about 0.948 to about 0.952 g/cm³ as determinedaccording to ASTM D 792; a melt index as determined according to ASTMD1238 (2.16 kg/190° C.) from about 16 to about 18 g/10 min; a weightaverage molecular weight (Mw) from about 48,000 to about 52,000; and apolydispersity from about 2.80 to about 2.90 and from about 40 to about20 weight % of an ethylene homopolymer having a density from about 0.960to about 0.965 g/cm³ as determined according to ASTM D 792; a melt indexas determined according to ASTM D1238 (2.16 kg/190° C.) from about 12 toabout 14 g/10 min, a weight average molecular weight (Mw) from about55,000 to about 63,000 and a polydispersity from about 3.15 to about3.25.

In a further embodiment, the polyethylene composition goes through notless than 900 cycles before breaking.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a GPC (Gel Permeation chromatography) of the blend of Example1

FIG. 2 is a GPC of the copolymer used in Example 1.

FIG. 3 is an A-TREF of the copolymer used in Example 1.

FIG. 4 is a GPC of the homopolymer used in Example 1.

FIG. 5 is an A-TREF of the homopolymer used in Example 1.

FIG. 6 is a front photograph of the bending strip tester used in theexperiments.

FIG. 7 is a side photograph of the bending strip tester used in theexperiments.

DETAILED DESCRIPTION

Other than in the operating examples or where otherwise indicated, allnumbers or expressions referring to quantities of ingredients, reactionconditions, etc. used in the specification, and claims are to beunderstood as modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that can vary depending upon the desired properties,which the present invention desires to obtain. At the very least, andnot as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques. Notwithstandingthat the numerical ranges and parameters setting forth the broad scopeof the invention are approximations, the numerical values set forth inthe specific examples are reported as precisely as possible. Anynumerical values, however, inherently contain certain errors necessarilyresulting from the standard deviation found in their respective testingmeasurements. Also, it should be understood that any numerical rangerecited herein is intended to include all sub-ranges subsumed therein.For example, the range 1 to 5 includes 2, 3, and 4 as well as thedecimal 2.1, 2.2, 2.3, . . . 4.8, 4.9 and the remaining decimal unitsbetween the end points indicated (e.g., 4.99993, 4.99994) and within thedecimal ranges indicated (2.29998, 2.29999 etc.). Because the disclosednumerical ranges are continuous, they include every value between theminimum and maximum values. Unless expressly indicated otherwise, thevarious numerical ranges specified in this application areapproximations. All compositional ranges expressed herein are limited intotal to and do not exceed 100 percent (volume percent or weightpercent) in practice. Where multiple components can be present in acomposition, the sum of the maximum amounts of each component can exceed100 percent, with the understanding that, and as those skilled in theart readily understand, that the amounts of the components actually usedwill conform to the maximum of 100 percent.

Snap top lids are typically made using an injection molding technique.For the polymer scientist this presents several conflicting desiderata.The polymer must have sufficient stiffness (flexural modulus) so thatthe parts (caps) do not deform when caps are being bulk shipped to anultimate customer. The polymer must have a melt index to permit it toquickly and completely fill the molds to make the parts (an appropriatecycle time for the part manufacturer). Finally, the polyethylene musthave a sufficient bending moment. That is it can be cycled through asufficient number of cycles through a radius of curvature of about 180to about 190° (e.g., 90° down and then 90° up).

For example, to improve stiffness, one would seek a higher densitypolymer. However, this would lower the number of bending cycles tofailure. One might consider increasing the molecular weight of thepolymer but this would likely negatively impact on the melt index, orthe ability to fill the mold quickly.

Embodiments of the polyethylene compositions described herein consist offrom about 0.1 to about 5 weight %, in other cases, from about 0.2 toabout 3 weight % of a C₄₋₈ comonomer (1-butene is a non-limitingexample), and the balance ethylene, said composition having a density asdetermined according to ASTM D 792 from about 0.945 to about 0.965g/cm³, in other cases from about 0.950 to about 0.960 g/cm³; a meltindex as determined according to ASTM D1238 (2.16 kg/190° C.) from about10 to about 20 g/10 min, in other cases from about 13 to about 17 g/10min; a weight average molecular weight (Mw) from about 45,000 to about55,000 g/mol, in other cases from about 48,000 to about 53,000 g/mol andin some situations from about 50,000 to about 52,000; a polydispersity(Mw/Mn) from about 2.5 to about 3.1, in other cases from 2.65 to 2.75and in some situations from about 2.68 to about 2.71; and when moldedinto a strip having a length of about 13 cm and a gross thickness fromabout 50 to about 70 mil (about 1 to about 2 mm) and completely bentover end to end four times (preferably twice in each direction (forwardsand backwards)) to create a thinned region or crease having a thicknessfrom about 15 to about 30 mil (about 0.3 to about 0.7 mm) tested bybending and releasing the deformed thinned region of the strip through aradius of curvature from about 180 to about 190° about a plate having arounded edge goes through not less than 200 cycles without breaking, insome cases greater than 750 cycles without breaking and in somesituations greater than 900 cycles without breaking.

The polyethylene composition may have a flex modulus as determined byASTM D 790 from about 1000 to about 1500 MPa (about 145,000 to about220,000 psi), in some cases from about 1200 to about 1400 MPa (about175,000 to about 200,000 psi). Polyethylene composition may have atensile strength at yield as determined by ASTM D638 (50 mm/min) fromabout 20 to about 30 MPa (about 3,000 to about 4,500 psi) preferablyfrom about 24 to about 28 MPa (about 3,600 to about 4,200 psi) and anelongation at break as determined according to ASTM D638 (50 mm/min)from about 500 to about 900%, typically from about 600 to about 800%.Generally, the softening point will be from about 120° to about 129° C.,typically from about 124° to about 127° C.

The comonomer placement in the composition is usually normal to flat.The term normal refers to a comonomer placement where there is a loweramount of comonomer incorporated in the higher molecular weight fractionof the composition; the term flat refers to a comonomer placement thatis approximately constant (flat) across the GPC molecular weightdistribution curve of the composition.

The polyethylene compositions described herein may be a blend of two ormore ethylene polymers; a non-limiting example is the blending of twoethylene polymers that are produced in a solution polymerizationprocess. The blend may be prepared in any suitable manner; anon-limiting example is dry blending (e.g., tumble blending) theethylene polymers and subsequent extrusion.

In one embodiment, such blends may comprise from about 60 to about 90weight %, in some cases from about 60 to about 80, in other instancesfrom 65 to about 75 weight % of an ethylene/1-butene copolymercontaining from about 0.1 to about 5 weight %, in some cases less thanabout 3 weight %, in other instances less than about 1.5 weight % of1-butene, having a density from about 0.945 to about 0.955 g/cm³ asdetermined according to ASTM D 792, in some cases from about 0.948 toabout 0.952 g/cm³; a melt index as determined according to ASTM D1238(2.16 kg/190° C.) from about 15 to about 20 g/10 min, in some cases fromabout 16 to about 18 g/10 min; a weight average molecular weight (Mw)from about 45,000 to about 55,000, in some cases from about 48,000 toabout 52,000, in other instances from about 49,000 to 51,000 g/mol; anda polydispersity from about 2.7 to about 3.0, in some cases from about2.8 to about 2.9, in other instances from about 2.84 to about 2.88.

The copolymer may have a flex modulus as determined by ASTM D 790 fromabout 900 to about 1200 MPa (about 130,000 to about 175,000 psi), insome cases from about 1000 to about 1100 MPa (about 145,000 to about160,000 psi).

The copolymer may have a tensile strength at yield as determined by ASTMD638 (50 mm/min) from about 22 to about 24 MPa (about 3,300 to about3,600 psi) and an elongation at break as determined according to ASTMD638 (50 mm/min) from about 500 to about 550%, in some cases from about520 to about 540%. Generally, the softening point will be about 118° C.to about 122° C., in some cases from about 119° C. to about 121° C.

In a further embodiment, the polyethylene composition comprises of fromabout 40 to about 10 weight %, in some cases, from about 40 to about 20weight %, in other instances, from about 35 to 25 weight % of anethylene homopolymer having a density from about 0.958 to about 0.965g/cm³ as determined according to ASTM D 792, in other cases, from about0.960 to about 0.963 g/cm³; a melt index as determined according to ASTMD1238 (2.16 kg/190° C.) from about 10 to about 15 g/10 min, in othercases, from about 12 to about 14 g/10 min, a weight average molecularweight (Mw) from about 55,000 to about 65,000, in some cases, from about56,000 to about 63,000, in other instances, from about 56,000 to about58,000 g/mol and a polydispersity from about 3.1 to about 3.3, in somecases from about 3.15 to about 3.25, in other instances, from about 3.15to about 3.20.

The homopolymer may have a flex modulus as determined by ASTM D 790 fromabout 1100 to about 1300 MPa (about 160,000 to about 190,000 psi), insome cases from about 1200 to about 1300 MPa (about 175,000 to about190,000 psi).

The homopolymer may have a tensile strength at yield as determined byASTM D638 (50 mm/min) from about 28 to about 34 MPa (about 4,050 toabout 4,900 psi), in some cases, from about 28 to about 32 MPa (about4,050 to about 4,600 psi) and an elongation at break as determinedaccording to ASTM D638 (50 mm/min) from about 700 to about 900%, in somecases, from about 750 to about 850%. Generally, the softening point willbe about 128° C. to about 131° C., in some cases, from about 129° C. toabout 130° C.

In another embodiment, the polyethylene composition comprises a blend ofthe above ethylene/1-butene copolymer and the ethylene homopolymer. Thisembodiment, or blend, may comprise from about 60 to about 90 weight %,in some cases, from about 60 to about 80 weight %, in other instances,from about 65 to about 75 weight % of the ethylene/1-butene copolymerand from about 40 to about 10 weight %, in some cases, from about 40 toabout 20 weight %, in other instances, from about 35 to about 25 weight% of the ethylene homopolymer.

The polyethylene polymers suitable for use in the present invention maybe prepared using conventional polymerization processes; non-limitingexamples include gas phase, slurry and solution polymerization. Thepolyethylenes may be prepared using conventional catalysts. Non-limitingexamples of conventional catalysts include; chrome based catalysts,Ziegler-Natta catalysts and single site catalysts. Such processes andcatalyst are well known to those skilled in the art.

Solution and slurry polymerization processes are fairly well known inthe art. These processes are conducted in the presence of an inerthydrocarbon solvent/diluent in some cases a C₄₋₁₂ hydrocarbon which maybe unsubstituted or substituted by a C₁₋₄ alkyl group, such as, butane,pentane, hexane, heptane, octane, cyclohexane, methylcyclohexane orhydrogenated naphtha. A non-limiting example of a commercial solvent isIsopar E (C₈₋₁₂ aliphatic solvent, Exxon Chemical Co.). The monomers aredissolved in the solvent/diluent.

The polymerization may be conducted at temperatures from about 20° C. toabout 250° C. Depending on the product being made, this temperature maybe relatively low such as from about 20° C. to about 180° C., in othercases, from about 80° C. to about 150° C. and the polymer is insolublein the liquid hydrocarbon phase (diluent) (e.g., a slurrypolymerization). The reaction temperature may be relatively higher fromabout 180° C. to about 250° C., in other cases, from about 180° C. toabout 230° C. and the polymer is soluble in the liquid hydrocarbon phase(solvent) (e.g., a solution polymerization). The pressure of thereaction may be as high as about 15,000 psig for the older high pressureprocesses or may range from about 15 to about 4,500 psig.

The polymerization could be gas phase, either fluidized bed or stirredbed. In the gas phase polymerization of a gaseous mixture comprisingfrom about 0 to about 15 mole % of hydrogen, from about 0 to about 30mole % of one or more C₃₋₈ alpha-olefins, from about 15 to about 100mole % of ethylene, and from about 0 to about 75 mole % of an inert gasat a temperature from about 50° C. to about 120° C., in some cases fromabout 75° C. to about 110° C., and at pressures not exceeding about 3447kPa (about 500 psi), in other cases not greater than about 2414 kPa(about 350 psi).

Suitable olefin monomers include ethylene and C₃₋₈ alpha olefins such asone or more of 1-butene, 1-hexene, and 1-octene. The polymers preparedin accordance with the present invention may have a wide range ofmolecular weight distribution (Mw/Mn or polydispersity). The molecularweight distribution may be controlled from about 2.5 to about 30.

In one embodiment, the polymers are solution polymers prepared in thepresence of a Ziegler-Natta catalyst; wherein the final compositioncomprises at least one copolymer of ethylene and 1-butene.

The resulting resin may typically be compounded either by themanufacturer or the converter (e.g., the company converting the resinpellets into the final product). The compounded polymer may containfillers, pigments and other additives. Typically, the fillers are inertadditives, such as, clay, talc, TiO₂ and calcium carbonate, which may beadded to the polyolefin in amounts from about 0 weight % up to about 50weight %, in some cases, less than 30 weight % of fillers are added. Theresin may contain typical amounts of antioxidants and heat and lightstabilizers, such as, combinations of one or more of hindered phenols,phosphates, phosphites and phosphonites, typically, in amounts of lessthan about 0.5 weight % based on the weight of the resin. Pigments mayalso be added to the resin in small amounts; non-limiting examples ofpigments include carbon black, phthalocyanine blue, Congo red, titaniumyellow, etc.

The polyethylene resin blend may contain a nucleating agent in amountsfrom about 1,500 parts per million (ppm) to about 10,000 ppm based onthe weight of the polyolefin. In some cases, the nucleating agent isused in amounts from about 2,000 ppm to about 8,000 ppm, in otherinstances, from about 2,000 ppm to about 5,000 ppm based on the weightof the polyolefin.

The nucleating agent may be selected from the group consisting ofdibenzylidene sorbitol, di(p-methyl benzylidene) sorbitol, di(o-methylbenzylidene) sorbitol, di(p-ethylbenzylidene) sorbitol, bis(3,4-dimethylbenzylidene) sorbitol, bis(3,4-diethylbenzylidene) sorbitol andbis(trimethyl-benzylidene) sorbitol. One commercially availablenucleating agent is bis(3,4-dimethyl benzylidene) sorbitol.

Since the resin is used in caps typically for food contact applications,the additive package must meet the appropriate food regulations, suchas, the FDA regulations in the United States.

The polymer is tested for the number of bend and release cycles bycompression molding a strip having thickness from about 50 to about 70mil (about 1 to about 2 mm) and a length of about 13 cm and completelybent over end to end and opened four times or cycles to create a thinnedregion or crease having a thickness from about 15 to about 30 mil (about0.3 to about 0.7 mm). The strip is mounted in a device as shown in FIG.6 with the thinned area or crease over or adjacent the edged of arounded plate (to avoid cutting the strip curing testing). The devicebends the strip over the edge of the plate through a radius of curvatureof about 180° to about 190° (i.e., one cycle is 90° up and then 90°down). The number of cycles until the test strip breaks is recorded.Generally, ten strips of the same polymer are tested at the same timeand the result is an average value until break.

The following example is intended to aid in understanding the presentinvention, however, in no way, should this example be interpreted aslimiting the scope thereof.

Example 1

The following resins were used in Example 1: SCLAIR® polyethylene resins2710 and 2909. SCLAIR 2710 is a copolymer of ethylene and about 0.35 wt.% of 1-butene. SCLAIR 2909 is a homopolymer of ethylene. The GPC curveand the A-TREF curves for copolymer SCLAIR 2710 are shown in FIGS. 2 and3, respectively. The GPC curve and the A-TREF curves for homopolymerSCLAIR 2909 are shown in FIGS. 4 and 5, respectively.

Table 1 summarizes the polymer properties.

TABLE 1 Test SCLAIR SCLAIR Method 2710 typical 2909 typical PropertyASTM Units values values Melt Index D 1238 g/10 min 17 13 Density D 792g/cm³ 0.915 0.962 Tensile Strength D 638 MPa (psi) 23 (3400) 29 (4200)at Yield 50 mm/min Elongation at D 638 % 530 800 break Flexural ModulusD 790 MPa (psi) 1000 (145000) 1280 (185000) Hardness Shore D D 2240 6265 Softening point D 1525 ° C. (° F.) 120 (248)  129 (264) 

The resins were tested in a blend, denoted Example 1, comprising 70 wt %of the copolymer and 30 weight % of the homopolymer. The GPC curve ofExample 1 is shown in FIG. 1.

Example 1 was molded into polymer strip samples as described above.

Polymer strip testing was done in a machine shown in FIGS. 6 and 7 inwhich like parts have like numbers. The machine generally shown at 1comprises a pair of pivoting disks 2 having there between a flat plate 3having a rounded edge or lip 4. On top of the plate are a series ofclamps 5 adjacent to edge or lip 4, which are attached to the plate 3.The test strips 6 are mounded on the plate 3 with clamps 5 andpositioned so that one end of the strip is held by a clamp. The creaseor thinned area is placed over the edge or lip 4. There is a bar 7mounted between the disks 2 which rests on top of the test strips 6inside of the rounded edge or lip 4. A further pair of bars 8 and 9 aremounted spaced apart between the disks 2. Disks 2 are driven byhydraulic pistons 10 and 11 (not shown) to cycle spaced apart bars 8 and9 through a radius of curvature from 90° above the plate 3 to 90° belowplate 3. The bars engage the end of the test strips 6 to bend themthrough each cycle. The number of cycles at which a test strip breaks isrecorded. Typically, 10 strips are tested at the same time and theaverage number of cycles to break is recorded. FIG. 7 shows hydraulicposition 10 attached to pivoting disk 2 (hydraulic piston 11 is notshown).

The results of the testing are set forth in Table 2 below.

TABLE 2 Strip Hinge Raw Data Cycles to Failure Date of Analysis March12/2013 Resin Grade: Blended 70% SCLAIR ® 2710/30% SCLAIR ® 2909Temperature: Ambient Lab Color: White Test Station 1 2 3 4 5 6 7 8 9 10min. 1032 1015 978 1824 1769 2493 650 1769 859 2086 max. 1165 1032 10151922 1824 2510 859 1824 873 2260 Overall Cycles to Ave. = 1487.95 Range:min. = 650 max. = 2510 Failure: notes: This sample was compressionmolded.

While the present invention has been particularly set forth in terms ofspecific embodiments thereof, it will be understood in view of theinstant disclosure that numerous variations upon the invention are nowenabled yet reside within the scope of the invention. Accordingly, theinvention is to be broadly construed and limited only by the scope andspirit of the claims now appended hereto.

What is claimed is:
 1. A polyethylene composition consisting of: i) from60 to 80 weight % of a polyethylene consisting of: from 0.1 to 0.5weight % of 1-butene and the balance ethylene; having a density asdetermined according to ASTM D 792 from 0.948 to 0.952 g/cm³; a meltindex as determined according to ASTM D1238 (2.16 kg, 190° C.) from 16to 18 g/10 min; a weight average molecular weight (Mw) from 48,000 to52,000 g/mol; a polydispersity from 2.7 to 3.0; and ii) from 40 to 20wt. % of a polyethylene homopolymer having a density from 0.960 g/cm³ to0.965 g/cm³; a melt index as determined according to ASTM D1238 (2.16kg, 190° C.) from 12 to 14 g/10 min, a weight average molecular weight(Mw) from 55,000 to 63,000 g/mol and a polydispersity from 3.0 to 3.3;wherein said composition having a density according to ASTM 792 from0.950 to 0.960 g/cm³, a tensile strength at yield from 24 to 28 MPa, anelongation at break as determined according to ASTM D638 from 500 to900%, and when molded into a strip having a length of 13 cm and grossthickness from 50 to 70 mil and completely bent over end to end fourtimes to create a creased strip having a thinned region having athickness from 15 to 30 mil, said creased strip tested in a bending andreleasing cycle until breaking wherein said thinned region is bent andreleased through a radius of curvature of 180° to 190° about a roundedplate until said creased strip breaks; said creased strip goes throughfrom about 650 to 2510 cycles prior to breaking.
 2. The polyethylenecomposition according to claim 1, wherein said creased strip goesthrough from about 750 to 2510 bending and releasing cycles beforebreaking.
 3. The polyethylene composition according to claim 1, whereinsaid creased strip goes through from about 900 to 2510 bending andreleasing cycles before breaking.